Overcurrent protection circuit

ABSTRACT

An overcurrent protection circuit includes a current control part configured to control conductance of a transistor so as to limit an output current flowing when the transistor is turned on to a predetermined upper limit or less, and a duty control part configured to forcibly turning on/off the transistor at a predetermined duty ratio when a temperature protection circuit detects a temperature abnormality in a state where the current control part limits the output current.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/672,958, filed Aug. 9, 2017 which claims the benefit of priority fromJapanese Patent Application No. 2016-157832, filed on Aug. 10, 2016, theentire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to an overcurrent protection circuit.

BACKGROUND

Conventionally, many semiconductor integrated circuit devices include anovercurrent protection circuit which is one of abnormality protectioncircuits. For example, an in-vehicle IPD (Intelligent Power Device)includes an overcurrent protection circuit so as to prevent the devicefrom being destroyed even when a load connected to a power transistor isshort-circuited.

By the way, there is also a load (a capacitive load, etc.) connected tothe power transistor that requires a large output currentinstantaneously in a normal operation. Therefore, the conventionalovercurrent protection circuit adopts a current control mode of limitingan output current to a predetermined upper limit value or less, insteadof cutting off the output current at the time of short-circuiting of theload, in which a determination on whether to cut off the output currentis delegated to a temperature protection circuit (a so-called thermalshutdown circuit) that detects a device temperature abnormality.

In many cases, the temperature protection circuit is of a self-resettingtype of forcibly turning off the power transistor when a junctiontemperature of the device is higher than an abnormality detection value(for example, 175 degrees C.) while releasing the forced-off of thepower transistor when the junction temperature is lower than anabnormality release value (for example, 150 degrees C.).

However, in the case of adopting the above-described conventionalabnormality protection method (the current control mode+theself-resetting type thermal shutdown), at the time of loadshort-circuit, the device will continue to operate in a high temperaturerange (for example, 150 degrees C. to 175 degrees C.) where thedetection and release of temperature abnormality with an overcurrent arerepeated. Therefore, there is a room for further improvement on thesafety of the device.

In particular, in recent years, it has been required to comply with ISO26262 (the international standards for electric/electronic-relatedfunctional safety of vehicles) for in-vehicle ICs and a higherreliability design becomes also important for in-vehicle IPD.

SUMMARY

Some embodiments of the present disclosure provide an overcurrentprotection circuit capable of securing an instantaneous current whileimproving safety.

According to an embodiment of the present disclosure, an overcurrentprotection circuit is provided. The overcurrent protection circuitincludes: a current control part configured to control conductance of atransistor so as to limit an output current flowing when the transistoris turned on to a predetermined upper limit or less; and a duty controlpart configured to forcibly turn on/off the transistor at apredetermined duty ratio when a temperature protection circuit detects atemperature abnormality in a state where the current control part limitsthe output current.

In some embodiments, the current control part may be configured tocompare a sense voltage corresponding to the output current with athreshold voltage corresponding to the upper limit and generate a firstovercurrent protection signal for controlling the conductance of thetransistor and a status notification signal for notifying the dutycontrol part of a state where the current control part limits the outputcurrent.

In some embodiments, the duty control part may include: a latch whichconfigured to switch and hold a pulse generation control signal from alogic level at the time of disabling to a logic level at the time ofenabling when the state notification signal is at a logic level at thetime of current limitation and a temperature protection signal is at alogic level at the time of abnormality detection; a pulse signalgeneration part configured to generate a pulse signal having the dutyratio while the pulse generation control signal is at the logic level atthe time of enabling; and a level shifter configured to generate asecond overcurrent protection signal for forcibly turning on/off thetransistor at the duty ratio by level-shifting the pulse signal.

In some embodiments, the pulse signal generation part may be configuredto continue generating the pulse signal until the pulse generationcontrol signal is reset to the logic level at the time of disabling.

According to another embodiment of the present disclosure, asemiconductor integrated circuit device is provided. The semiconductorintegrated circuit device includes: a transistor configured toconduct/interrupt a current path through which an output current flows;a gate control part configured to generate a driving signal of thetransistor in response to a control signal; a temperature protectioncircuit configured to detect a temperature abnormality of the device;and the overcurrent protection circuit.

In some embodiments, the temperature protection circuit may beconfigured to monitor a temperature of the transistor and detect atemperature abnormality.

In some embodiments, a first temperature detecting element for detectingthe temperature of the transistor may be disposed near a pad of thetransistor within a formation region of the transistor.

In some embodiments, the temperature protection circuit may be formedadjacent to the transistor and the first temperature detecting elementis disposed near a corner closest to the temperature protection circuitamong four corners of the pad.

In some embodiments, the temperature protection circuit may beconfigured to monitor a temperature difference between a temperature ofthe transistor and a temperature of another integrated circuit anddetect a temperature abnormality.

In some embodiments, the temperature protection circuit may be formedadjacent to the transistor and a second temperature detecting elementfor detecting the temperature of the another integrated circuit may bedisposed in a formation region of the temperature protection circuit.

According to another embodiment of the present disclosure, an electronicapparatus is provided. The electronic apparatus includes thesemiconductor integrated circuit device, and a load connected to thesemiconductor integrated circuit device.

In some embodiments, the load may be a bulb lamp, a relay coil, asolenoid, a light emitting diode or a motor. According to anotherembodiment of the present disclosure, a vehicle including the electronicapparatus is provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a semiconductor integrated circuitdevice according to a first embodiment.

FIG. 2 is a block diagram showing a configuration example of a gatecontrol part.

FIG. 3 is a circuit diagram showing a configuration example of atemperature protection circuit.

FIG. 4 is a view for explaining an operation of generating a temperatureprotection signal.

FIG. 5 is a block diagram showing a configuration example of anovercurrent protection circuit.

FIG. 6 is a circuit diagram showing a configuration example of a currentcontrol part.

FIG. 7 is a circuit diagram showing a modification of the currentcontrol part.

FIG. 8 is a circuit diagram showing a configuration example of a dutycontrol part.

FIG. 9 is a circuit diagram showing a configuration example of a pulsesignal generator.

FIG. 10 is a timing chart showing an example of an overcurrentprotection operation.

FIG. 11 is a flowchart showing an example of an overcurrent protectionoperation.

FIG. 12 is a block diagram showing a modification of the temperatureprotection circuit.

FIG. 13 is a block diagram showing a semiconductor integrated circuitdevice according to a second embodiment.

FIG. 14 is a block diagram showing an example of introduction of amultiplexer.

FIG. 15 is a layout diagram of a semiconductor integrated circuitdevice.

FIG. 16 is an external view showing a configuration example of avehicle.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be now described in detailwith reference to the drawings. Like or equivalent components, members,and processes illustrated in each drawing are given like referencenumerals and a repeated description thereof will be properly omitted.Further, the embodiments are presented by way of example only, and arenot intended to limit the present disclosure, and any feature orcombination thereof described in the embodiments may not necessarily beessential to the present disclosure.

Semiconductor Integrated Circuit Device (First Embodiment

FIG. 1 is a block diagram showing a semiconductor integrated circuitdevice according to a first embodiment. The semiconductor integratedcircuit device 1 of this embodiment includes an in-vehicle high-sideswitch IC (which is a type of the in-vehicle IPD) thatconnects/disconnects between the application terminal of a power supplyvoltage VBB and a load 3 according to an instruction from an ECU(Electronic Control Unit) 2.

The semiconductor integrated circuit device 1 includes externalterminals T1 to T4 for establishing electrical connection with theexternal of the device. The external terminal T1 is a power supplyterminal (VBB pin) for receiving the power supply voltage VBB (forexample, 12V) from a battery (not shown). The external terminal T2 is aload connection terminal (OUT pin) for externally connecting the load 3(a bulb lamp, a relay coil, a solenoid, a light emitting diode, a motor,etc.). The external terminal T3 is a signal input terminal (IN pin) forreceiving an external input of an external control signal Si from theECU 2. The external terminal T4 is a signal output terminal (SENSE pin)for externally outputting a status signal So to the ECU 2. An externalsense resistor 4 is externally connected between the external terminalT4 and the ground terminal.

The semiconductor integrated circuit device 1 includes an NMOSFET 10, anoutput current monitoring part 20, a gate control part 30, a controllogic part 40, a signal input part 50, an internal power supply part 60,an abnormality protection part 70, an output current detection part 80and a signal output part 90.

The NMOSFET 10 is a high-breakdown voltage (for example, 42V breakdownvoltage) power transistor having a drain connected to the externalterminal T1 and a source connected to the external terminal T2. TheNMOSFET 10 thus connected functions as a switch element (high-sideswitch) for connecting/disconnecting a current path ranging from theapplication terminal of the power supply voltage VBB to the groundterminal via the load 3. The NMOSFET 10 is turned on when the gatedriving signal G1 is at a high level, and is turned off when the gatedriving signal G1 is at a low level.

The NMOSFET 10 may be designed so that its on-resistance value isseveral tens of mΩ. However, the lower the on-resistance value of theNMOSFET 10, the more likely it is for an overcurrent to flow at the timeof ground fault of the external terminal T2 (i.e., at the time ofshort-circuit to the ground terminal or an equivalent low potentialterminal), which may result in generation of abnormal heat. Therefore,as the on-resistance value of the NMOSFET 10 becomes lower and lower, anovercurrent protection circuit 71 and a temperature protection circuit73 to be described later are of more importance.

The output current monitoring part 20 includes NMOSFETs 21 and 21′ and asense resistor 22 and generates a sense voltage Vs corresponding to anoutput current Io flowing through the NMOSFET 10.

Both of the NMOSFETs 21 and 21′ are mirror transistors connected inparallel to the NMOSFET 10 and generate sense currents Is and Is′respectively according to the output current Io. The size ratio betweenthe NMOSFET 10 and the NMOSFETs 21 and 21′ is m:1 (where m>1).Therefore, the sense currents Is and Is′ are equal to 1/m of the outputcurrent Io. Like the NMOSFET 10, the NMOSFETs 21 and 21′ are turned onwhen the gate driving signal G1 is at a high level, and are turned offwhen the gate voltage G1 is at a low level.

The sense resistor 22 (its resistance: Rs) is connected between thesource of the NMOSFET 21 and the external terminal T2 and is acurrent/voltage conversion element that generates a sense voltage Vs(=Is×Rs+Vo, where Vo represents an output voltage appearing on theexternal terminal T2) corresponding to the sense current Is.

The gate control part 30 generates the gate drive signal G1 with theincreased current capability of the gate control signal S1 and outputsthe gate drive signal G1 to the gates of the NMOSFETs 10 and 21, therebycontrolling the turning-on/off of the NMOSFETs 10 and 21.

The control logic part 40 receives an internal power supply voltage Vregand generates the gate control signal S1. For example, when the externalcontrol signal Si is at a high level (a logic level when turning on theNMOSFET 10), since the internal power supply voltage Vreg is suppliedfrom the internal power supply part 60, the control logic part 40 entersan operation state and the gate control signal S1 has a high level(=Vreg). On the other hand, when the external control signal Si is at alow level (a logic level when turning off the NMOSFET 10), since theinternal power supply voltage Vreg is not supplied from the internalpower supply part 60, the control logic part 40 enters a non-operatingstate and the gate control signal S1 has a low level (=GND). Inaddition, the control logic part 40 monitors various abnormalityprotection signals (an overcurrent protection signal S71, an openprotection signal S72, a temperature protection signal S73 and a reducedvoltage protection signal S74). The control logic unit 40 also has afunction of generating an output switching signal S2 based on a resultof the monitoring on the overcurrent protection signal S71, the openprotection signal S72 and the temperature protection signal S73 amongthe aforementioned abnormality protection signals.

The signal input part 50 is a Schmitt trigger that receives the externalcontrol signal Si from the external terminal T3 and transmits it to theinternal power supply part 60. The external control signal Si is at ahigh level when the NMOSFET 10 is turned on, and is at a low level whenthe NMOSFET 10 is turned off.

The internal power supply part 60 generates a predetermined internalpower supply voltage Vreg from the power supply voltage VBB and suppliesit to each of the parts of the semiconductor integrated circuit device1. Whether or not the internal power supply part 60 is operable iscontrolled according to the external control signal Si. Morespecifically, the internal power supply part 60 is in an operating statewhen the external control signal Si is at a high level, and is in anon-operating state when the external control signal Si is at a lowlevel.

The abnormality protection part 70 is a circuit block for detectingvarious abnormalities of the semiconductor integrated circuit device 1and includes an overcurrent protection circuit 71, an open protectioncircuit 72, a temperature protection circuit 73 and a reduced voltageprotection circuit 74.

The overcurrent protection circuit 71 generates the overcurrentprotection signal S71 based on a result of monitoring on the sensevoltage Vs (i.e., based on a determination on whether or not anovercurrent abnormality of the output current Io occurs). For example,the overcurrent protection signal S71 has a low level when noabnormality is detected, and has a high level when an abnormality isdetected.

The open protection circuit 72 generates the open protection signal S72based on a result of monitoring on the output voltage Vo (i.e., based ona determination on whether or not an open abnormality of the load 3occurs). For example, the open protection signal S72 has a low levelwhen no abnormality is detected, and has a high level when anabnormality is detected.

The temperature protection circuit 73 includes a temperature detectionelement (not shown) for detecting a temperature abnormality in thesemiconductor integrated circuit device 1 (particularly inside or nearthe NMOSFET 10) and generates the temperature protection signal S73based on a result of the detection (i.e., based on a determination onwhether or not a temperature abnormality occurs). For example, thetemperature protection signal S73 has a low level when no abnormality isdetected, and has a high level when an abnormality is detected.

The reduced voltage protection circuit 74 generates the reduced voltageprotection signal S74 based on a result of monitoring on the powersupply voltage VBB or the internal power supply voltage Vreg (i.e.,based on a determination on whether or not a reduced voltage abnormalityoccurs). For example, the reduced voltage protection signal S74 has alow level when no abnormality is detected, and has a high level when anabnormality is detected.

The output current detection part 80 generates a sense current Is′(=Io/m) corresponding to the output current Io by matching the sourcevoltage of the NMOSFET 21′ with the output voltage Vo using a bias means(not shown) and outputs it to the signal output part 90.

Based on the output selection signal S2, the signal output unit 90selectively outputs one of the sense current Is′ (corresponding to thedetection result of the output current Io) and a fixed voltage V90(corresponding to an abnormality flag, which is not explicitly shown inthis figure) to the external terminal T4. When the sense current Is′ isselected and outputted, an output detection voltage V80 (=Is′×R4)obtained by current/voltage conversion of the sense current Is′ with theexternal sense resistor 4 (its resistance: R4) is transmitted as thestatus signal So to the ECU2. The output detection voltage V80 increaseswith the increase in the output current Io and decreases with thedecrease in the output current Io. On the other hand, when the fixedvoltage V90 is selected and outputted, the fixed voltage V90 istransmitted as the status signal So to the ECU 2. In this embodiment,the fixed voltage V90 may be set to a voltage value higher than theupper limit value of the output detection voltage V80.

According to such a signal output unit 90, both the detection result ofthe output current to and the abnormality flag can be transmitted to theECU 2 by using the single status signal So, contributing to thereduction in the number of external terminals. When reading a currentvalue of the output current Io out of the status signal So, ananalog-to-digital (A/D) conversion may be performed on the status signalSo. On the other hand, when reading the abnormality flag out of thestatus signal So, the logic level of the status signal So may bedetermined using a threshold value slightly lower than the fixed voltageV90.

<Gate Control Part>

FIG. 2 is a block diagram showing a configuration example of the gatecontrol part 30 and the peripheral portion thereof. The gate controlpart 30 of this configuration example includes a gate driver 31, anoscillator 32, a charge pump 33, a clamper 34, NMOSFETs 35 and 36, aresistor 37 (its resistance: R37) and a capacitor 38 (its capacitance:C38).

The gate driver 31 is connected between the output terminal of thecharge pump 33 (the application terminal of a boosted voltage VG) andthe external terminal T2 (the application terminal of the output voltageVo) and generates the gate driving signal G1 with the increased currentcapability of the gate control signal S1. Basically, the gate drivingsignal G1 has a high level (=VG) when the gate control signal S1 is at ahigh level, and has a low level (=Vo) when the gate control signal S1 isat a low level.

The oscillator 32 generates a clock signal CLK of a predeterminedfrequency and outputs it to the charge pump 33. Whether or not theoscillator 32 is operable is controlled according to an enable signal Safrom the control logic part 40.

The charge pump 33 generates the boosted voltage VG higher than thepower supply voltage VBB by driving a flying capacitor (not shown) usingthe clock signal CLK. Whether or not the charge pump 33 is operable iscontrolled according to an enable signal Sb from the control logic part40.

The clamper 34 is connected between the external terminal T1 (theapplication terminal of the power supply voltage VBB) and the gate ofthe NMOSFET 10. In an application in which an inductive load 3 isconnected to the external terminal T2, the output voltage Vo becomes anegative voltage (<GND) due to a counter electromotive force of the load3 when switching the NMOSFET 10 from ON to OFF. Therefore, the clamper34 (a so-called active clamp circuit) is provided for energy absorption.

The drain of the NMOSFET 35 is connected to the gate of the NMOSFET 10.The source of the NMOSFET 35 is connected to the external terminal T2. Afirst overcurrent protection signal S71 a (corresponding to theearlier-described overcurrent protection signal S71) is applied from theovercurrent protection circuit 71 to the gate of the NMOSFET 35. Theresistor 37 and the capacitor 38 are connected in series between thedrain and the gate of the NMOSFET 35.

The drain of the NMOSFET 36 is connected to the gate of the NMOSFET 10.The source of the NMOSFET 36 is connected to the external terminal T2. Asecond overcurrent protection signal S71 b is applied from theovercurrent protection circuit 71 to the gate of the NMOSFET 36.However, unlike the NMOSFET 35, neither a resistor nor a capacitor isconnected between the drain and the gate of the NMOSFET 36.

In the gate control part 30 of this configuration example, the NMOSFET35 is turned off when the first overcurrent protection signal S71 a isat a low level (a logic level at the time of abnormality non-detection),and is turned on when the first overcurrent protection signal S71 a isat a high level (a logic level at the time of abnormality detection).Accordingly, when the first overcurrent protection signal S71 a rises tothe high level, the gate driving signal G1 is pulled down from thesteady-state high level (=VG) with a predetermined time constantτ(=R37×C38). As a result, conductance of the NMOSFET 10 graduallydecreases to limit the output current Io. On the other hand, when thefirst overcurrent protection signal S71 a falls to the low level, thegate driving signal G1 is pulled up with the predetermined time constantτ. As a result, the conductance of the NMOSFET 10 gradually increases tocancel the limitation of the output current Io.

Further, the NMOSFET 36 is turned off when the second overcurrentprotection signal S71 b is at a low level (a logic level at the time ofcancellation of forced-off), and is turned on when the secondovercurrent protection signal S71 b is at a high level (a logic level atthe time of forced-off). Accordingly, when the second overcurrentprotection signal S71 b rises to the high level, since the gate and thesource of the NMOSFET 10 are short-circuited, the NMOSFET 10 is forciblyturned off and the output current Io is interrupted without delay. Onthe other hand, when the second overcurrent protection signal S71 bfalls to the low level, the gate and the source of the NMOSFET 10 aredisconnected from each other, the forced-off of the NMOSFET 10 iscanceled.

As described above, the overcurrent protection circuit 71 of thisconfiguration example employs two control methods thereof, i.e., acurrent control mode for controlling the conductance of the NMOSFET 10using the first overcurrent protection signal S71 a and a duty controlmode for forcibly turning on/off the NMOSFET 10 using the secondovercurrent protection signal S71 b, and is configured to switch fromthe current control mode to the duty control mode in response to thetemperature protection signal S73 input from the temperature protectioncircuit 73.

In the following description, structures and operations of thetemperature protection circuit 73 and the overcurrent protection circuit71 will be sequentially described in detail.

<Temperature Protection Circuit>

FIG. 3 is a circuit diagram showing a configuration example of thetemperature protection circuit 73. The temperature protection circuit 73of this configuration example is a circuit block for detecting atemperature abnormality by monitoring a junction temperature Tj insideor near the NMOSFET 10 and includes current sources 101 and 102, aresistor 103, a diode array 104 and a comparator 105.

The first terminals of the current sources 101 and 102 and the powersupply potential terminal of the comparator 105 are both connected tothe application terminal of the internal power supply voltage Vreg. Thesecond terminal of the current source 101 and the first terminal of theresistor 103 are both connected to the non-inverting input terminal (+)of the comparator 105. The second terminal of the current source 102 andthe anode terminal of the diode array 104 are both connected to theinverting input terminal (−) of the comparator 105. The second terminalof the resistor 103, the cathode terminal of the diode array 104 and thereference potential terminal of the comparator 105 are all connected tothe ground terminal GND. The output terminal of the comparator 105corresponds to the output terminal of the temperature protection signalS73.

Each of the current sources 101 and 102 generates a predeterminedreference current Iref when the external control signal Si is at a highlevel.

The diode array 104 may be provided at a position where the junctiontemperature Tj inside or near the NMOSFET 10 can be detected. In theexample of this figure, the number of serial stages of diodes formingthe diode array 104 is four. However, this is merely an example and thenumber of serial stages of diodes is arbitrary.

The comparator 105 compares a node voltage V1 (a constant voltage havinga temperature characteristic of zero or near zero) input to anon-inverting input terminal (+) and a node voltage V2 (an anode voltageof the diode array 104 having the negative temperature characteristic)input to an inverting input terminal (−), thereby generating thetemperature protection signal S73. The temperature protection signal S73has a high level (a logic level when a temperature abnormality isdetected. Vreg) when the node voltage V1 is higher than the node voltageV2, and has a low level (a logic level when no temperature abnormalityis detected, GND) when the node voltage V is lower than the node voltageV2.

In addition, the comparator 105 may have a hysteresis characteristic.For example, the input stage of the comparator 105 may be controlledsuch that the node voltage V1 and the node voltage V2 are compared witheach other when the temperature protection signal S73 is at the lowlevel, and an addition voltage (V1+Vhys), which is obtained by adding ahysteresis voltage Vhys to the node voltage V1, and the node voltage V2are compared with each other when the temperature protection signal S73is at the high level.

FIG. 4 is a view for explaining an operation of generating thetemperature protection signal S73, in which the node voltages V1 and V2and the temperature protection signal S73 are depicted in order from thetop. In this figure, the horizontal axis represents the junctiontemperature Tj.

When the temperature protection signal S73 is at the low level, thecomparator 105 is in a state of comparing the node voltage V1 and thenode voltage V2. In such a state, when the junction temperature Tj ishigher than an upper threshold temperature TthH (for example, 175degrees C.) and the node voltage V2 is lower than the node voltage V1,the temperature protection signal S73 rises to the high level.

On the other hand, when the temperature protection signal S73 is at thehigh level, the comparator 105 is in a state of comparing the additionvoltage (V1+Vhys), which is obtained by adding the hysteresis voltageVhys to the node voltage V1, and the node voltage V2. In such a state,when the junction temperature Tj is lower than a lower thresholdtemperature TthL (for example, 150 degrees C.) and the node voltage V2is higher than the addition voltage (V1+Vhys), the temperatureprotection signal S73 falls to the low level.

<Overcurrent Protection Circuit>

FIG. 5 is a block diagram showing a configuration example of theovercurrent protection circuit 71. The overcurrent protection circuit 71of this configuration example includes a current control part 110 and aduty control part 120.

The current control part 110 compares the sense voltage Vs(corresponding to the output current Io) with a predetermined thresholdvoltage Vth (corresponding to the upper limit value of the outputcurrent Io, not shown in this figure) to generate the first overcurrentprotection signal S71 a for controlling the conductance of the NMOSFET10. Based on a result of the comparison, the current control part 110has a function to generate a state notification signal S110 fornotifying the duty control part 120 of a state where the current controlpart 110 limits the output current Io (S71 a=H).

The duty control part 120 receives the state notification signal S110and the temperature protection signal S73 and generates the secondovercurrent protection signal S71 b. More specifically, when thetemperature protection circuit 73 detects a temperature abnormality(S73=H) in a state where the current control part 110 limits the outputcurrent Io (S110=H), the duty control part 120 starts to generate apulse of the second overcurrent protection signal S71 b and forciblyturns on/off the NMOSFET 10 at a predetermined duty ratio Don.

Hereinafter, the circuit configurations and operations of theabove-described functional parts will be described in more detail.

<Current Control Part>

FIG. 6 is a circuit diagram showing a configuration example of thecurrent control part 110. The current control part 110 of thisconfiguration example includes a current source 111, a resistor 112(resistance: Rref), a comparator 113, an NMOSFET 114. PMOSFETs 115 and116, a depletion type NMOSFET 117 and a Zener diode 118.

A first terminal of the current source 111 and a power supply potentialterminal of the comparator 113 are both connected to the applicationterminal of the boosted voltage VG. A second terminal of the currentsource 111 and a first terminal of the resistor 112 are both connectedto an inverting input terminal (−) of the comparator 113. The sensevoltage Vs is input to the non-inverting input terminal (+) of thecomparator 113. The second terminal of the resistor 112 and a referencepotential terminal of the comparator 113 are both connected to theapplication terminal of the output voltage Vo. An output terminal of thecomparator 113 corresponds to the output terminal of the firstovercurrent protection signal S71 a.

A gate of the NMOSFET 114 is connected to an output terminal of thecomparator 113. A source of the NMOSFET 114 is connected to theapplication terminal of the output voltage Vo. A drain of the NMOSFET114 is connected to a drain of the PMOSFET 115. Each of the sources ofthe PMOSFETs 115 and 116 is connected to the application terminal of theboosted voltage VG. Each of the gates of the PMOSFETs 115 and 116 isconnected to the drain of the PMOSFET 115. A drain of the PMOSFET 116 isconnected to a drain of the NMOSFET 117 and a cathode of the Zener diode118. A gate and a source of the NMOSFET 117 and an anode of the Zenerdiode 118 are both connected to the ground terminal GND. The drain ofthe PMOSFET 116 corresponds to the output terminal of the statenotification signal S110.

The current source 1 generates a predetermined reference current Irefand supplies it to the resistor 112. Accordingly, a predeterminedthreshold voltage Vth (=Iref×Rref) is input to the inverting inputterminal (−) of the comparator 113. A voltage value of the thresholdvoltage Vth may be determined according to the upper limit value of theoutput current Io.

The comparator 113 compares the sense voltage Vs input to thenon-inverting input terminal (+) with the threshold voltage Vth input tothe inverting input terminal (−) to generate the first overcurrentprotection signal S71 a. The first overcurrent protection signal S71 ahas a low level (a logic level when no abnormality is detected) when thesense voltage Vs is lower than the threshold voltage Vth, and has a highlevel (a logic level when an abnormality is detected) when the sensevoltage Vs is higher than the threshold voltage Vth.

The NMOSFET 114 is turned off when the first overcurrent protectionsignal S71 a is at the low level, and is turned on when the firstovercurrent protection signal S71 a is at the high level. The PMOSFETs115 and 116 form a current mirror and mirror a drain current Id1 of thePMOSFET 115 to generate a drain current 1 d 2 of the PMOSFET 116. Thedepletion type NMOSFET 117 functions as a constant current source sinceits gate and source are interconnected. The Zener diode 118 functions asa clamping element for limiting the upper limit value of the statusnotification signal S110.

In the current control part 110 of this configuration example, since theNMOSFET 114 is turned off when the first overcurrent protection signalS71 a is at the low level, a current path ranging from the drain of thePMOSFET 115 to the application terminal of the output voltage Vo isinterrupted. Accordingly, the drain currents Id1 and Id2 do not flow andthe state notification signal S110 has a low level (a logic level whenthe limitation of the output current Io is released).

On the other hand, since the NMOSFET 114 is turned on when the firstovercurrent protection signal S71 a is at the high level, the abovecurrent path is in a conducting state. Accordingly, since the draincurrents Id1 and Id2 flow, the state notification signal S110 has a highlevel (a logic level when the output current Io is limited).

FIG. 7 is a circuit diagram showing a modification of the currentcontrol part 110. The current control part 110 of this modificationincludes NMOSFETs 113 a and 113 b and a current source 113 c as circuitelements that replace the comparator 113, based on the circuitconfiguration of FIG. 6.

The first terminals of the current sources 111 and 113 c is connected tothe application terminal of the boosted voltage VG. The second terminalof the current source 111 is connected to a drain of the NMOSFET 113 a.A second terminal of the current source 113 c is connected to a drain ofthe NMOSFET 113 b. A source of the NMOSFET 113 a is connected to thefirst terminal of the resistor 112. The second terminal of the resistor112 is connected to the application terminal of the output voltage Vo.Gates of the NMOSFET 113 a and 113 b are both connected to the drain ofthe NMOSFET 113 a. The sense voltage Vs is applied to a source of theNMOSFET 113 b. The drain of the NMOSFET 113 b corresponds to the outputterminal of the first overcurrent protection signal S71 a.

In this way, the current control part 110 may employ a comparatorcircuit using a current mirror as a circuit element which replaces thecomparator 113 of FIG. 6.

<Duty Control Part>

FIG. 8 is a circuit diagram showing a configuration example of the dutycontrol part 120. The duty control part 120 of this configurationexample includes an AND operator 121, an RS flip-flop 122, a pulsesignal generator 123 and a level shifter 124.

The AND operator 121 generates an AND signal S121 by performing an ANDoperation of the state notification signal S110 and the temperatureprotection signal S73. The AND signal S121 has a high level when thestate notification signal S110 and the temperature protection signal S73are both at a high level, and has a low level when at least one of thestate notification signal S110 and the temperature protection signal S73is at a low level. That is, the AND signal S121 has a high level onlywhen the state notification signal S110 is at a high level (a logiclevel at the time of current limitation) and the temperature protectionsignal S73 has a high level (a logic level at the time of abnormalitydetection).

The RS flip-flop 122 is a latch that switches a logic level of a pulsegeneration control signal S122 output from an output terminal (Q),according to the AND signal S121 input to a set terminal (S) and theexternal control signal Si input to a reset terminal (R).

For example, the RS flip-flop 122 sets the pulse generation controlsignal S122 at a high level (a logic level at the time of enabling) whenthe AND signal S121 rises to a high level, and resets the pulsegeneration control signal S122 at a low level (a logic level at the timeof disabling) when the external control signal Si falls to a low level.

The pulse signal generator 123 generates a pulse signal S123 of the dutyratio Don over a high level period of the pulse generation controlsignal S122.

The level shifter 124 generates the second overcurrent protection signalS71 b for forcibly turning on/off the NMOSFET at the duty ratio Don bylevel-shifting the pulse signal S123.

<Pulse Signal Generator>

FIG. 9 is a circuit diagram showing a configuration example of the pulsesignal generator 123. The pulse signal generator 123 of thisconfiguration example includes NMOSFETs N1 to N3, PMOSFETs P1 to P3,current sources CS1 and CS2, a capacitor C1, resistors R1 to R3,comparators CMP1 and CMP2, an RS flip-flop FF1 and an AND operator AND1.

Sources of the PMOSFETs P1 to P3 are all connected to the applicationterminal of the internal power supply voltage Vreg. Drains of thePMOSFETs P1 and P2 are both connected to a first terminal of the currentsource CS1. A second terminal of the current source CS1 is connected tothe ground terminal GND. Gates of the PMOSFETs P2 and P3 are bothconnected to a drain of the PMOSFET P2.

Sources of the NMOSFETs N1 to N3 are both connected to the groundterminal GND. A first terminal of the current source CS2 is connected tothe application terminal of the internal power supply voltage Vreg. Asecond terminal of the current source CS2 is connected to drains of theNMOSFETs N1 and N2. The gates of the NMOSFETs N2 and N3 are bothconnected to the drain of the NMOSFET N2.

A drain of the PMOSFET P3 and the drain of the NMOSFET N3 are bothconnected to a first terminal of a capacitor C1. A second terminal ofthe capacitor C1 is connected to the ground terminal.

Gates of the PMOSFET P1 and the NMOSFET N1 are both connected to anoutput terminal of the pulse signal S123. Accordingly, when the pulsesignal S123 is at a high level, the PMOSFET P1 is turned off and theNMOSFET N1 is turned on. Conversely, when the pulse signal S123 is at alow level, the PMOSFET P1 is turned on and the NMOSFET N1 is turned off.

When the PMOSFET P1 is turned off and the NMOSFET N1 is turned on, anupper current mirror including the PMOSFETs P2 and P3 becomes effectiveand a lower current mirror composed of the NMOSFETs N2 and N3 becomesineffective. Accordingly, the capacitor C1 is charged with a chargingcurrent Ic (more accurately, a drain current of the PMOSFET P3 mirroringthe charging current Ic) generated by the current source CS1.

On the other hand, when the PMOSFET P1 is turned on and the NMOSFET N1is turned off, the upper current mirror becomes ineffective and thelower current mirror becomes effective. Accordingly, the capacitor C1 isdischarged with a discharging current Id (more accurately, a draincurrent of the NMOSFET N3 mirroring the discharging current Id)generated by the current source CS2.

The resistors R1 to R3 are connected in series between the applicationterminal of the internal power supply voltage Vreg and the groundterminal GND. A connection node between the resistors R1 and R2corresponds to an output terminal of an upper threshold voltage VH(=Vreg×(R2+R3)/(R1+R2+R3)) and a connection node between the resistorsR2 and R3 corresponds to an output terminal of a lower threshold voltageVL (=Vreg×R3/(R1+R2+R3)). In this way, the resistors R1 to R3 functionas a voltage divider for dividing the internal power supply voltage Vregto generate the upper threshold voltage VH and the lower thresholdvoltage VL (<VH).

Power supply potential terminals of the comparators CMP1 and CMP2 areboth connected to the application terminal of the internal power supplyvoltage Vreg. Reference potential terminals of the comparators CMP1 andCMP2 are both connected to the ground terminal GND. Non-inverting inputterminals (+) of the comparators CMP1 and CMP2 are both connected to thefirst terminal (an output terminal of a charging voltage Vp) of thecapacitor C1. Inverting input terminal (−) of the comparator CMP1 isconnected to the connection node (an output terminal of the upperthreshold voltage VH) between the resistors R1 and R2. Inverting inputterminal (−) of the comparator CMP2 is connected to the connection node(an output terminal of the lower threshold voltage VL) between theresistors R2 and R3.

The comparator CMP1 compares the charging voltage Vp with the upperthreshold voltage VH, thereby generating an upper comparison signal SH.The upper comparison signal SH has a high level (=Vreg) when thecharging voltage Vp is higher than the upper threshold voltage VH, andhas a low level (=GND) when the charging voltage Vp is lower than theupper threshold voltage VH.

The comparator CMP2 compares the charging voltage Vp with the lowerthreshold voltage VL, thereby generating a lower comparison signal SL.The lower comparison signal SL has a high level (=Vreg) when thecharging voltage Vp is higher than the lower threshold voltage VL, andhas a low level (=GND) when the charging voltage Vp is lower than thelower threshold voltage VL.

The RS flip-flop FF1 has a latch that switches a logic level of a latchoutput signal SO output from an inverting output terminal (QB),according to the upper comparison signal SH input to a set terminal (S)and the lower comparison signal SL input to a reset terminal (R).

For example, the RS flip-flop FF 1 sets the latch output signal SO at alow level (a logic level at the time of cancellation of forced-off) whenthe upper comparison signal SH rises to a high level, and resets thelatch output signal SO at a high level (a logic level at the time offorced-off) when the lower comparison signal SL falls to a low level. Inthis case, the latch output signal SO is a square wave signal having alow level when the charging voltage Vp rises to the upper thresholdvoltage VH and having a high level when the charging voltage Vp drops tothe lower threshold voltage VL.

The AND operator AND1 generates the pulse signal S123 by performing anAND operation of the pulse generation control signal S122 and the latchoutput signal SO. The pulse signal S123 has a high level when the pulsegeneration control signal S122 and the latch output signal SO are bothat a high level, and has a low level when at least one of the pulsegeneration control signal S122 and the latch output signal SO is at alow level. That is, when the pulse generation control signal S122 is ata high level (a logic level at the time of enabling), the latch outputsignal SO is through-outputted as the pulse signal S123. On the otherhand, when the pulse generation control signal S122 is at a low level (alogic level at the time of disabling), the pulse signal S123 is fixed ata low level without depending on the logic level of the latch outputsignal SO.

<Overcurrent Protection Operation>

FIG. 10 is a timing chart showing an example of the overcurrentprotection operation, in which the external control signal Si, the sensevoltage Vs, the state notification signal S110, the junction temperatureTj, the temperature protection signal S73, the pulse generation controlsignal S122, the charging voltage Vp, the upper comparison signal SH,the lower comparison signal SL, the latch output signal SO and the pulsesignal S123 are depicted in order from the top.

At time t1, when the external control signal Si rises to a high level,the generation operation of the reference current Iref (not shown inthis figure) starts without delay and the semiconductor integratedcircuit device 1 enters a standby state. However, at time t1, sinceshutdown of the semiconductor integrated circuit device 1 is notreleased and the NMOSFET 10 is kept off, the output current to does notflow to the NMOSFET 10. Accordingly, the sense voltage Vs is kept at 0V.

At time t2, when a predetermined activation delay period Tdly (e.g., 5μs) elapses from time t1, the shutdown of the semiconductor integratedcircuit device 1 is released. As a result, since the NMOSFET 10 isturned on and the output current Io starts to flow, the sense voltage Vsstarts to rise. In this figure, the RS flip-flop FF1 is activated atthis point and the latch output signal SO rises to the high level, butsince the pulse generation control signal S122 is kept at the low level,the pulse signal S123 is also kept at the low level. Accordingly, sincethe capacitor C1 is discharged with the discharging current Id, thecharging voltage Vp is kept at 0V.

After that, the output current Io continues to increase and, at time t3,when the sense voltage Vs becomes higher than the threshold voltage Vth,the output current Io is limited below the upper limit value by thecurrent control mode described above. At this time, the statenotification signal S110 rises to a high level (a logic level at thetime of current limitation), but since the junction temperature Tj islower than the upper threshold temperature TthH, the temperatureprotection signal S73 remains at a low level. Accordingly, the pulsegeneration control signal S122 is kept at the low level.

In this way, as long as no temperature abnormality is detected, aninstantaneous current at start-up can be secured if overcurrentprotection by the current control mode is applied. Accordingly, forexample, when a bulb lamp as the load 3 is connected, it is possible tosufficiently warm up and activate the bulb lamp.

On the other hand, since the output current Io is maintained near theupper limit value when the load is short-circuited, the NMOSFET 10continues to generate heat. As a result, at time t4, the junctiontemperature Tj becomes higher than the upper threshold temperature TthHand the temperature protection signal S73 rises to a high level.

In this manner, when both the state notification signal S110 and thetemperature protection signal S73 go to the high level, since the pulsegeneration control signal S122 rises to the high level, the latch outputsignal SO as the pulse signal S123 is through-output. The latch outputsignal SO is already at the high level at this time. Accordingly, thepulse signal S23 rises to the high level without delay at the point oftime when the pulse generation control signal S122 rises to a highlevel.

When the pulse signal S123 rises to the high level, the MOSFET 10 isforcibly turned off. Accordingly, since the output current Io does notflow and the sense voltage Vs decreases to 0V, the status notificationsignal S110 falls to a low level. However, the pulse generation controlsignal S122 remains at the high level. In addition, as the MOSFET 10 isforcibly turned off, the junction temperature Tj changes from rising tofalling. In addition, since the charging of the capacitor C1 with thecharging current Ic starts, the charging voltage Vp starts to rise.

At time t5, when the charging voltage Vp becomes higher than the lowerthreshold voltage VL the lower comparison signal SL rises to a highlevel, but the logic level of the latch output signal SO does notchange.

At time t6, when the junction temperature Tj becomes lower than thelower threshold temperature TthL, the temperature protection signal S73falls to a low level. However, the pulse generation control signal S122is still maintained at the high level.

At time t7, when the charging voltage Vp rises to the upper thresholdvoltage VH, the upper comparison signal SH rises to a high level.Accordingly, since the latch output signal SO is set at a low level, thepulse signal S123 also falls to a low level. As a result, since theforced-off of the MOSFET 10 is released and the output current Io startsto flow again, the sense voltage Vs and the junction temperature Tj turnto rise. In addition, since the discharging of the capacitor C1 with thedischarging current Id starts, the charging voltage Vp starts todecrease.

At time t8, when the charging voltage Vp drops to the lower thresholdvoltage VL, the lower comparison signal SL falls to a low level.Accordingly, since the latch output signal SO is reset to a high level,the pulse signal S123 also rises to a high level. As a result, since theMOSFET 10 is again forcibly turned off, the sense voltage Vs drops to 0Vand the junction temperature Tj changes from rising to falling. Inaddition, since the charging of the capacitor C1 with the chargingcurrent Ic resumes, the charging voltage Vp starts to increase.

At time t9, when the charging voltage Vp rises again to the upperthreshold voltage VH, the upper comparison signal SH rises to the highlevel, the latch output signal SO is set to the low level, and the pulsesignal S123 falls to the low level. As a result, since the forced-off ofthe MOSFET 10 is released, the sense voltage Vs and the junctiontemperature Tj turn to rise. In addition, since the discharging of thecapacitor C1 with the discharging current Id starts, the chargingvoltage Vp starts to decrease. This operation is exactly the same as theoperation at time t7.

Even after time t9, similarly to the above, the pulse signal S123alternates between the high level period and the low level period. Attime t10, when the external control signal Si falls to a low level, thesemiconductor integrated circuit device 1 is shut down to complete theabove-described series of operations.

With attention on the pulse generation operation after time t4, the lowlevel period (for example, time t7 to time t8) of the pulse signal S123corresponds to the ON period Ton (the forced-off release period) of theNMOSFET 10 and the high level period (for example, time t8 to time t9)of the pulse signal S123 corresponds to the OFF period Toff (theforced-off period) of the NMOSFET 10.

That is, after time t4, the NMOSFET 10 alternates between the ON periodTon and the OFF period Toff at a predetermined duty ratio Don (Ton/T,where T=Ton+Toff). In other words, the overcurrent protection circuit 71switches from the current control mode to the duty control mode aftertime t4.

The duty ratio Don may be set so that the junction temperature Tj surelydecreases to a safe temperature range after time t4. For example, whenDon is set to 4% (Ton=20 to 30 μs and Toff=500 to 700 μs), after timet4, unlike the conventional self-reset type thermal shutdown (see thebroken line in the figure), the junction temperature Tj will not bemaintained at a high temperature range (150 to 175 degrees C.) but canbe lowered to a sufficiently safe temperature range (about 70 to 80degrees C.), thereby enhancing the safety of the semiconductorintegrated circuit device 1.

In particular, it can be said that the above-described duty control modeis a very effective control method for clearing a reliability testpeculiar to in-vehicle equipment (for example, a load short reliabilitytest (AEC (Automotive Electronics Council) Q100-012 for evaluatingsafety at the time of output terminal short-circuit or ground fault).

In addition, when the overcurrent protection by the current control modeis performed until a temperature abnormality is detected, and then theovercurrent protection by the duty control mode is performed after thetemperature abnormality is detected, it is possible to achieve bothinstantaneous current securing and safety improvement, so that it ispossible to flexibly cope with various specifications of the load 3 andalso to clear the functional safety required for the semiconductorintegrated circuit device 1 at a high level.

At time t4, after the pulse generation control signal S122 rises to thehigh level and the current control mode is switched to the duty controlmode, the generation operation of the pulse signal S123 is continueduntil the external control signal Si falls to a low level and the pulsegeneration control signal S122 is reset to a low level (a logic level atthe time of disabling). That is, once the current control mode isswitched to the duty control mode, there is no return to the currentcontrol mode until the semiconductor integrated circuit device 1 isrestarted (Si=L→H).

FIG. 11 is a flowchart showing an example of the overcurrent protectionoperation. When this flow starts, first, in step S101, it is determinedwhether or not the sense voltage Vs is higher than the threshold voltageVth. If a YES determination is made in this step, the flow proceeds tostep S102. On the other hand, if a NO determination is made, the flowreturns to step S101 and the determination in this step is repeated(which corresponds to times t1 to t3 in FIG. 10).

In step S102, upon receiving the YES determination in step S101, theoutput current Io is limited to a predetermined upper limit value orless by the current control mode (which corresponds to times t3 to t4 inFIG. 10).

In the subsequent step S103, it is determined whether or not thejunction temperature Tj is higher than the threshold temperature Tth. Ifa YES determination is made in this step, the flow proceeds to stepS104. On the other hand, if a NO determination is made, the flow returnsto step S101 (which corresponds to times t3 to t4 in FIG. 10).

In step S104, the NMOSFET 10 is forcibly turned off in response to theYES determination in step S103 (which corresponds to time t4 in FIG.10).

In step S105, the capacitor C1 starts to be charged and the chargingvoltage Vp starts to rise (which corresponds to time t4 in FIG. 10).

In the subsequent step S106, it is determined whether or not thecharging voltage Vp rises to the upper threshold voltage VH. If a YESdetermination is made in this step, the flow proceeds to step S107. Onthe other hand, if a NO determination is made, the flow returns to stepS105 in which the charging of the capacitor C is continued (whichcorresponds to times t4 to t7 in FIG. 10).

In step S107, in response to the YES determination in step S106, theforced-off of the NMOSFET 10 is released (which corresponds to time t7in FIG. 10).

In step S108, the capacitor C1 starts to be discharged and the chargingvoltage Vp starts to drop (which corresponds to time t7 in FIG. 10).

In the subsequent step S109, it is determined whether or not thecharging voltage Vp drops to the lower threshold voltage VL. If a NOdetermination is made in this step, the flow returns to step S108 andthe charging of the capacitor C1 is continued (which corresponds totimes t7 to t8 in FIG. 10). On the other hand, if a YES determination ismade, the flow returns to step S104 and the NMOSFET 10 is again forciblyturned off (which corresponds to time t8).

That is, by repeating steps S104 to S109, the overcurrent protection bythe above-described duty control mode is applied.

<Temperature Protection Circuit (Modification)>

FIG. 12 is a block diagram showing a modification of the temperatureprotection circuit 73. The temperature protection circuit 73 accordingto this modification includes a first temperature detector 73A, a secondtemperature detector 73B and an OR operator 73C.

The first temperature detector 73A detects a junction temperature Tj1 ofthe NMOSFET 10 by using a temperature detecting element D1 providedinside or near the NMOSFET 10 and compares it with a predetermined upperlimit temperature Tth (for example, 175 degrees C.) to generate a firsttemperature protection signal S73A. The first temperature protectionsignal S73A has a low level (a logic level when no abnormality isdetected) when the junction temperature Tj1 is lower than the upperlimit temperature Tth. and has a high level (a logic level when anabnormality is detected) when the junction temperature Tj1 is higherthan the upper limit temperature Tth. That is, it can be said that thefirst temperature detector 73A corresponds to the above-describedtemperature protection circuit 73 shown in FIG. 3.

The second temperature detector 73B detects a junction temperature Tj2of an integrated circuit 100 (the control logic part 40 or the like) byusing a temperature detecting element D2 provided inside or near theintegrated circuit 100 excluding the NMOSFET 10 and compares atemperature difference ΔTj (=Tj1-Tj2) between the junction temperatureTj1 and the junction temperature Tj2 with a predetermined upper limittemperature difference ΔTth (for example, 60 degrees C.) to generate asecond temperature protection signal S73B. The second temperatureprotection signal S73B has a low level (a logic level when noabnormality is detected) when the temperature difference ΔTj is smallerthan the upper limit temperature difference ΔTth, and has a high level(a logic level when an abnormality is detected) when the temperaturedifference ΔTj is larger than the upper limit temperature differenceΔTth.

The OR operator 73C generates a third temperature protection signal S73Cby performing an OR operation of the first temperature protection signalS73A and the second temperature protection signal S73B. The thirdtemperature protection signal S73C has a low level when both the firsttemperature protection signal S73A and the second temperature protectionsignal S73B are at a low level, and has a high level when at least oneof the first temperature protection signal S73A and the secondtemperature protection signal S73B is at a high level. The thirdtemperature protection signal S73C is output to the overcurrentprotection circuit 71 (particularly, the duty control part 120), insteadof the above-described temperature protection signal S73 (see FIGS. 2,5, 8, etc.).

By adopting the temperature protection circuit 73 of this modification,the overcurrent protection circuit 71 can be switched from the currentcontrol mode to the duty control mode not only when an abnormality ofthe junction temperature Tj1 is detected (S73A=H) but also when anabnormality of the temperature difference ΔTj is detected (S73B=H).

Semiconductor Integrated Circuit Device (Second Embodiment)

FIG. 13 is a block diagram showing a semiconductor integrated circuitdevice according to a second embodiment. The semiconductor integratedcircuit device 1 of this embodiment has the above-described constituentelements (the functional blocks 10 to 90, the external terminals T1 toT3, various voltages, currents and signals, etc.) for each channel,based on the first embodiment (FIG. 1), in order to individually drivetwo-channel loads 3X and 3Y.

“X” is appended to the end of the symbol for the constituent elementsrelated to the driving of the load 3X and “Y” is appended to the end ofthe symbol for the constituent elements related to the driving of theload 3Y but the operations and functions thereof are basically the sameas the above-mentioned constituent elements not appended with “X” and“Y” at the end. For example, the operations and functions of NMOSFETs10X and 10Y are basically the same as that of the aforementioned NMOSFET10. The same applies to other constituent elements. In this figure, forconvenience of illustration, output current detectors 80X and 80Y andsignal output parts 90X and 90Y are not explicitly shown, but thesefunctional blocks will be described in detail together with amultiplexer to be described below.

<Multiplexer>

FIG. 14 is a block diagram showing an example in which a multiplexer isintroduced as an output stage of the status signal So with thetwo-channelization of the semiconductor integrated circuit device 1described so far. In the semiconductor integrated circuit device 1 ofthis configuration example, the output current detectors 80X and 80Y,the signal output parts 90X and 90Y, the multiplexer 130 and an externalterminal T5 are integrated.

The output current detector 80X generates a sense current IsX′corresponding to an output current IoX and outputs it to the signaloutput part 90X.

The output current detector 80Y generates a sense current IsY′corresponding to an output current IoY and outputs it to the signaloutput part 90Y.

The signal output part 90X includes a selector 91X that selectivelyoutputs one of the sense current IsX′(corresponding to a result ofdetection of the output current IoX) and a fixed voltage V90(corresponding to an abnormality flag) as a first status signal SoXbased on an output selection signal S2X input from a control logic part40X. The selector 91X selectively outputs the sense current IsX′ as thefirst status signal SoX when the output selection signal S2X is at alogic level (for example, low level) when no abnormality is detected,and outputs the fixed voltage V90 as the first status signal SoX whenthe output selection signal S2X is at a logic level (for example, highlevel) when an abnormality is detected.

The signal output part 90Y includes a selector 91Y that selectivelyoutputs one of the sense current IsY′(corresponding to a result ofdetection of the output current IoY) and the fixed voltage V90(corresponding to the abnormality flag) as a second status signal SoYbased on an output selection signal S2Y input from a control logic part40Y. The selector 91Y selectively outputs the sense current IsY′ as thesecond status signal SoY when the output selection signal S2Y is at alogic level (for example, low level) when no abnormality is detected,and outputs the fixed voltage V90 as the second status signal SoY whenthe output selection signal S2Y is at a logic level (for example, highlevel) when an abnormality is detected.

In response to an output selection signal SEL input to the externalterminal T5, the multiplexer 130 selectively outputs one of a firststatus signal SoX (the sense current IsX′ or the fixed voltage V90) anda second status signal SoY (the sense current IsY′ or the fixed voltageV90) to the external terminal T4.

When the sense current IsX′ is selectively output to the externalterminal T4, an output detection voltage V80X (=IsX′×R4) obtained bycurrent-voltage conversion of the sense current IsX′ by the externalsense resistor 4 is output as the status signal So to the ECU 2. Theoutput detection voltage V80X increases with the increase in the outputcurrent IoX and decreases with the decrease in the output current IoX.

When the sense current IsY′ is selectively output to the externalterminal T4, an output detection voltage V80Y (=IsY′×R4) obtained bycurrent/voltage conversion of the sense current IsY′ by the externalsense resistor 4 is output as the status signal So to the ECU 2. Theoutput detection voltage V80Y increases with the increase in the outputcurrent IoY and decreases with the decrease in the output current IoY.

On the other hand, when the fixed voltage V90 is selectively output tothe external terminal T4, it is transmitted as the status signal So tothe ECU 2. The fixed voltage V90 may be set to a voltage value higherthan the upper limit values of the output detection voltages V80X andV80Y.

With the introduction of such a multiplexer 130, it is possible toexternally monitor both the detection results of the output currents IoXand IoY and the abnormality flag for an arbitrary channel.

<IC Layout>

FIG. 15 is a layout of the two-channel semiconductor integrated circuitdevice 1. As shown in this figure, power MOSFETs (corresponding to theNMOSFETs 10X and 10Y in FIG. 13) of each channel are arranged not on thecentral portion but on the side portion of the chip. The power MOSFETsof each channel are formed in an L shape when viewed from top. This iscommon as a shape for increasing the resistance against inductive loadssuch as inductors.

A driver DRV (corresponding to the gate control parts 30X and 30Y inFIG. 13) and a temperature protection circuit TSD/ΔTj (corresponding tothe temperature protection circuit 73 in FIG. 12) of each channel areformed in the central portion of the chip, which are surrounded by thepower MOSFETs of the channel or other circuit elements.

It is desirable that the temperature detection element D1 for detectingthe temperature of the power MOSFET be disposed in a place where heat ismost likely to be concentrated in a formation region of the powerMOSFET. In simple terms, it seems that this place is the central portionof the power MOSFET, but in reality, a point where the heatconcentration is most likely to occur is determined depending on thelayout of pads and the area of the power MOSFET. In the example of thisfigure, since the power MOSFET has two channels, in consideration ofleft and right uniformity and ease of layout wiring, the temperaturedetecting element D1 is located near the pads of the power MOSFET (inparticular, near a corner closest to the temperature protection circuitTSD/ΔTj among four corners of the pads) and the position of the pads areadjusted so that the heat generation is most concentrated at thelocation.

In addition, it is unnecessary to keep the temperature detecting elementD2 for detecting the temperature of the integrated circuit other thanthe power MOSFET away from the power MOSFET, but rather, the temperaturedetecting element D2 may be disposed near the power MOSFET in view ofdetection accuracy. In the example of this figure, the temperaturedetecting element D2 is disposed within the formation region of thetemperature protection circuit TSD/ΔTj adjacent to the power MOSFET. Thetemperature of the power MOSFET rises quickly when the power MOSFET isturned on to flow a current, and falls when the power MOSFET is turnedoff. On the other hand, the temperature of the temperature protectioncircuit TSD/ΔTj gradually changes due to the heat generation of thepower MOSFET. In the temperature protection circuit TSD/ΔTj(particularly the second temperature detector 73B in FIG. 12), atemperature difference between them is monitored.

<Applications to Vehicle>

FIG. 16 is an external view showing a configuration example of avehicle. The vehicle X of this configuration example is equipped with abattery (not shown in the drawing) and various electronic apparatusesX11 to X18 which are operated with power supplied from the battery. Themounting positions of the electronic apparatuses X11 to X18 in thisfigure may be different from the actual positions for convenience ofillustration.

The electronic apparatus X11 is an engine control unit that performsengine-related control (injection control, electronic throttle control,idling control, oxygen sensor heater control, auto cruise control,etc.).

The electronic apparatus X12 is a lamp control unit that performs on/offcontrol of HID (High Intensity Discharged lamp) or DRL (Daytime RunningLamp).

The electronic apparatus X13 is a transmission control unit thatperforms transmission-related control.

The electronic apparatus X14 is a body control unit that performscontrol related to the motion of the vehicle X (ABS (Anti-lock BrakeSystem) control, EPS (Electric Power Steering) control, electronicsuspension control, etc.).

The electronic apparatus X15 is a security control unit that performscontrol of driving of a door lock, a security alarm, etc.

The electronic apparatus X16 is an electronic apparatus incorporated inthe vehicle X at the factory shipment stage as standard equipment or amaker optional item such as a wiper, an electric door mirror, a powerwindow, a damper (a shock absorber), an electric sunroof, an electricseat, and the like.

The electronic apparatus X17 is an electronic apparatus that isoptionally mounted on the vehicle X as a user optional item such as anin-vehicle AN (Audio/Visual) device, a car navigation system, an ETC(Electronic Toll Collection system), and the like.

The electronic apparatus X18 is an electronic apparatus including ahigh-voltage resistant motor such as an in-vehicle blower, an oil pump,a water pump, a battery cooling fan, and the like.

The semiconductor integrated circuit device 1, the ECU 2 and the load 3described above can be incorporated in any of the electronic apparatusesX11 to X18.

Other Modifications

Further, in the above embodiments, the description has been given takingthe in-vehicle high-side switch IC as an example, but the presentdisclosure is not limited thereto. For example, the present disclosurecan be widely applied not only to other in-vehicle IPD (in-vehiclelow-side switch ICs, in-vehicle power supply ICs, etc.) but also tosemiconductor integrated circuit devices other than vehicleapplications.

INDUSTRIAL APPLICABILITY

The present disclosure can be used for, for example, an in-vehicle IPD(such as an in-vehicle switch having high versatility).

According to the present disclosure in some embodiments, it is possibleto provide an overcurrent protection circuit capable of securing aninstantaneous current while improving safety.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosures. Indeed, the embodiments described herein maybe embodied in a variety of other forms. Furthermore, various omissions,substitutions and changes in the form of the embodiments describedherein may be made without departing from the spirit of the disclosures.The accompanying claims and their equivalents are intended to cover suchforms or modifications as would fall within the scope and spirit of thedisclosures.

What is claimed is:
 1. An overcurrent protection circuit comprising: acurrent controller configured to control conductance of a transistor tolimit a flowing output current to a predetermined upper limit or lesswhile keeping the transistor turned on; and a duty controller configuredto forcibly turn on/off the transistor at a predetermined duty ratiowhen a temperature protection circuit detects a temperature abnormality,wherein the current controller is further configured to: compare a sensevoltage corresponding to the output current with a threshold voltagecorresponding to the predetermined upper limit; and generate a firstovercurrent protection signal configured to control the conductance ofthe transistor and a state notification signal configured to notify theduty controller of a state where the current controller limits theoutput current, wherein the duty controller includes: a latch configuredto switch and hold a pulse generation control signal from a logic levelat the time of disabling to a logic level at the time of enabling whenthe state notification signal is at a logic level at the time of currentlimitation and a temperature protection signal is at a logic level atthe time of abnormality detection; a pulse signal generator configuredto generate a pulse signal having the duty ratio while the pulsegeneration control signal is at the logic level at the time of enabling;and a level shifter configured to generate a second overcurrentprotection signal configured to forcibly turn on/off the transistor atthe duty ratio by level-shifting the pulse signal.
 2. The overcurrentprotection circuit of claim 1, wherein the transistor is forcibly turnedon/off at the predetermined duty ratio when the temperature abnormalityis detected in a state where the output current is limited.
 3. Theovercurrent protection circuit of claim 1, wherein the transistor iskept turned on when the transistor does not limit the output current. 4.The overcurrent protection circuit of claim 1, wherein the pulse signalgenerator is configured to continue generating the pulse signal untilthe pulse generation control signal is reset to the logic level at thetime of disabling.
 5. A semiconductor integrated circuit devicecomprising: a transistor configured to conduct/interrupt a current paththrough which an output current flows; a gate controller configured togenerate a driving signal of the transistor in response to a controlsignal; a temperature protection circuit configured to detect atemperature abnormality of the device; and the overcurrent protectioncircuit of claim
 1. 6. The semiconductor integrated circuit device ofclaim 5, wherein the temperature protection circuit is configured tomonitor a temperature of the transistor and detect a temperatureabnormality.
 7. A semiconductor integrated circuit device comprising: atransistor configured to conduct/interrupt a current path through whichan output current flows; a gate controller configured to generate adriving signal of the transistor in response to a control signal; atemperature protection circuit configured to monitor a temperature ofthe transistor and to detect a temperature abnormality of the device,wherein a first temperature detecting element for detecting thetemperature of the transistor is disposed near a pad of the transistorwithin a formation region of the transistor; and an overcurrentprotection circuit comprising: a current controller configured tocontrol conductance of the transistor to limit the output current to apredetermined upper limit or less while keeping the transistor turnedon; and a duty controller configured to forcibly turn on/off thetransistor at a predetermined duty ratio when the temperature protectioncircuit detects the temperature abnormality.
 8. The semiconductorintegrated circuit device of claim 7, wherein the temperature protectioncircuit is formed adjacent to the transistor and the first temperaturedetecting element is disposed near a corner closest to the temperatureprotection circuit among four corners of the pad.
 9. A semiconductorintegrated circuit device comprising: a transistor configured toconduct/interrupt a current path through which an output current flows;a gate controller configured to generate a driving signal of thetransistor in response to a control signal; a temperature protectioncircuit configured to monitor a temperature difference between atemperature of the transistor and a temperature of another integratedcircuit and to detect a temperature abnormality of the device; and anovercurrent protection circuit comprising: a current controllerconfigured to control conductance of the transistor to limit the outputcurrent to a predetermined upper limit or less while keeping thetransistor turned on; and a duty controller configured to forcibly turnon/off the transistor at a predetermined duty ratio when the temperatureprotection circuit detects the temperature abnormality.
 10. Thesemiconductor integrated circuit device of claim 9, wherein thetemperature protection circuit is formed adjacent to the transistor, andwherein a temperature detecting element configured to detect thetemperature of the other integrated circuit is disposed in a formationregion of the temperature protection circuit.
 11. An electronicapparatus comprising: the semiconductor integrated circuit device ofclaim 5; and a load connected to the semiconductor integrated circuitdevice.
 12. The electronic apparatus of claim 11, wherein the load is abulb lamp, a relay coil, a solenoid, a light emitting diode or a motor.13. A vehicle comprising the electronic apparatus of claim 11.